Field of the Invention
The invention lies in the telecommunications and data transmission fields and relates, more specifically, to the operation of a data transmission system comprising an active partner, also called master, a passive partner, also called slave, and comprising redundant data transmission paths which are also called communication channels. The invention relates especially to the operation of a data transmission system for the higher-level control of a resource platform in network interconnections for telecommunications.
In the field of distributed intelligent networks, one or more dependent computers or data processing facilities (referred to as resource platform), which are to be controlled, can be connected to a higher-level control computer, which is also called “service node controller” (master) by means of a node architecture (so-called “service node architecture”). The master is the computer executing the actual control functions, on which a service, to be implemented, for example, for telephone callers, is programmed. In the context of the present invention, the term ‘service’ includes a sequencing logic which provides a caller with a particular service (e.g. an information service which is menu-controlled by telephone key input). A resource platform is usually connected to the public switched telephone network (PSTN) and is used for implementing simple functions (such as short announcements, output or input acknowledgment, e.g. of data generated by key operation). Furthermore, during the telecommunication from the resource platform, the message of calls arriving at the platform via a multiplicity of telephone lines can also be signaled to the master.
The communication between master and slave requires interface definitions which regulate the exchange of messages between master and slave. For this purpose, various specifications are known such as, for example, from GTE Telephone Operations, 700 Hidden Ridge Irving, Tex., with the designation “Intelligent Peripheral Resource Platform Interface (IP-RPI)”. The messages are usually exchanged on the basis of network protocols, whereby the TCP/IP protocol is widely used (TCP/IP=Transport Control Protocol/Internet Protocol. In principle, however, other protocols can also be used. Communication between master and slave can take place, for example, via a local area network (LAN). According to the above-mentioned specification by the company GTE, no redundancies are provided for these network connections (LAN connections). This has a fatal effect on the communication between master and slave when the LAN connection is faulty. If the LAN connection is interrupted temporarily or for a longer time (for example by destruction of the connecting cable), communication between master and slave, and thus, for example in a telecommunications system, the acceptance and processing of incoming telephone calls, is no longer possible.
In view of this background, it is conceivable to reserve a second or further LAN connections (LAN redundancy) for the sake of safety, to which it is possible to switch, if necessary, if the LAN connection hitherto used is faulty. However, the procedure required for the switchover is relatively elaborate and, due to system conditions, must accept at least a temporary loss of data in the phase in which the faulty condition of the previously used LAN connection is detected, processed further and finally switched over to an alternative LAN connection.